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Characterisation of a novel cellobiose 2‐epimerase from thermophilic Caldicellulosiruptor obsidiansis for lactulose production
Author(s) -
Chen Qiuming,
Levin Roman,
Zhang Wenli,
Zhang Tao,
Jiang Bo,
Stressler Timo,
Fischer Lutz,
Mu Wanmeng
Publication year - 2016
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.8148
Subject(s) - lactulose , lactose , cellobiose , chemistry , food science , substrate (aquarium) , thermostability , biochemistry , enzyme , cellulase , biology , ecology
BACKGROUND Lactulose, a bioactive lactose derivative, has been widely used in food and pharmaceutical industries. Isomerisation of lactose to lactulose by cellobiose 2‐epimerase ( CE ) has recently attracted increasing attention, since CE produces lactulose with high yield from lactose as a single substrate. In this study, a new lactulose‐producing CE from Caldicellulosiruptor obsidiansis was extensively characterised. RESULTS The recombinant enzyme exhibited maximal activity at pH 7.5 and 70 °C. It displayed high thermostability with T m of 86.7 °C. The half‐life was calculated to be 8.1, 2.8 and 0.6 h at 75, 80, and 85 °C, respectively. When lactose was used as substrate, epilactose was rapidly produced in a short period, and afterwards both epilactose and lactose were steadily isomerised to lactulose, with a final ratio of 35:11:54 for lactose:epilactose:lactulose. When the reverse reaction was investigated using lactulose as substrate, both lactose and epilactose appeared to be steadily produced from the start. CONCLUSION The recombinant CE showed both epimerisation and isomerisation activities against lactose, making it an alternative promising biocatalyst candidate for lactulose production. © 2016 Society of Chemical Industry